JP2008068586A - Method and apparatus for molding resin molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding method of a resin molded product capable of enhancing filling properties when a foamable resin is adapted to the injection molding of a blow molded product having a skin material, and a molding apparatus of the resin molded product. <P>SOLUTION: The molding apparatus of the resin molded product is equipped with a parison suspending means, a mold clamping means, a blow shaping means, an injection port forming means 5 for blowing through the part connected to the foamable resin injection passage 3d of the parison P from the inside to the outside by the gas B used in blow shaping to form the injection port P9 of the foamable resin 36 and an injection means for leaving the parison P in a cavity 2a in a blow-shaped state and injecting the molten foamable resin 36 in the foamable resin injection passage 3d to inject the same in the parison P through the injection port P9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a molding method and a molding apparatus for a resin molded product, and more particularly to injection molding in which a molten foamable resin is injected and filled into a cavity.

  In recent years, resin products made of a foamable resin for the purpose of weight reduction and the like are being used frequently. As one form of the molding method, there is an injection molding in which a molten foamable resin is injection-filled into a cavity (a space formed by a mold).

  Since a thin skin layer (solid layer that does not foam) is formed on the surface of the foamable resin molded product obtained by injection molding, a smooth surface can be obtained. However, since the skin layer is a very thin layer, the foamed portion near the surface layer may break up until the molded product is solidified, and bubbles may be exposed on the surface through the skin layer. When this molded article requires a beautiful surface, such exposure of bubbles is not preferable.

  Further, improvement of physical properties (rigidity, etc.) may be required depending on the usage of the molded product.

  Therefore, in order to meet the demand for enhancing the aesthetics of the surface or improving the physical properties, resin molded products having a non-foaming skin provided on the surface layer have been studied. By providing a non-foaming skin on the molded product, air bubbles are not exposed on the surface, so the aesthetics are improved. Moreover, necessary physical properties can be easily obtained by appropriately setting the material and thickness of the skin.

  On the other hand, blow molding is known as one form of resin molding. Blow molding is a mold-shaped hollow molding in which a thermoplastic resin (parison) molded into a cylindrical shape by an extruder or the like is sandwiched between molds to form a bag, and air or the like is blown into it to inflate it. This is a molding method for obtaining a product.

As a skin material of an expandable resin molded product, one using this blow molded product is known (see, for example, Patent Document 1). However, what is shown in Patent Document 1 is a method in which a blow molded hollow molded product is filled with foamed particles, steam is supplied to the foamed particles and heated and fused. It is applied to different molding methods.
JP 2004-284149 A

  It seems that the technique shown in Patent Document 1 can be applied to injection molding. However, in order to inject and fill the foamable resin into the blown parison, there is a specific problem that an injection port must be provided at an appropriate position of the parison.

  That is, for example, a method in which a blow-molded hollow molded article is once taken out of a mold, and once again set in a mold for injection molding after the injection port is drilled, is extremely inefficient, and when blow molding is performed. Although it is conceivable to use the blow pin mark as an injection port, it is difficult to lay out the apparatus, which naturally complicates and enlarges the apparatus.

  In view of such circumstances, in the present invention, in foamable resin molding using a blow-molded product as a skin material, this is also applied to injection molding, and it is easy to foam inside the parison while having a simple structure. An object of the present invention is to provide a molding method and molding apparatus for a resin molded product that can inject a functional resin.

  The invention according to claim 1 for solving the above-described problem is a method for molding a resin molded product having an interior made of a foamable resin and a surface layer portion made of a solid resin, wherein the parison is suspended from the parison of the solid resin. A mold with a foamable resin injection passage for guiding the melted foamable resin into the cavity, and a mold clamping step for forming a bag shape with the suspended parison interposed therebetween, and the inside of the bagged parison A blow molding step for inflating the parison into a shape along the cavity shape of the mold, and a gas used in the blow shaping step after the blow shaping step is completed. Blowing through the part connected to the foamable resin injection passage from the inside to the outside, the injection port forming step for forming the foamable resin injection port, and the parison remains blow-shaped Allowed to remain in the cavity, the molten foamable resin is injected into the foamable resin injection passage, characterized in that via the inlet including an injection step of injecting into the parison.

  In this specification, solid resin refers to non-foaming resin.

  According to a second aspect of the present invention, in the method for molding a resin molded article according to the first aspect, the foamable resin injection passage is provided with an injection passage valve that expands a cavity volume by moving the valve body. In the inlet forming step, the inlet is formed by expanding the cavity volume by the injection passage valve while maintaining the air pressure in the parison.

  According to a third aspect of the present invention, in the method for molding a resin molded article according to the second aspect, the injection passage valve moves in a state where the foamable resin injection passage is opened, a first closed state where the foamable resin injection passage is closed, and a valve body. As a result, it is possible to switch from the first closed state to the second closed state in which the cavity volume is enlarged, and in the blow shaping step, the first closed state is set and the injection port is formed. In the process, the second closed state is set, and in the injection process, the open state is set.

  According to a fourth aspect of the present invention, in the method for molding a resin molded product according to any one of the first to third aspects, the molding die includes a throttle portion for thinning a parison at a location where the injection port is formed. It is characterized by having.

  According to a fifth aspect of the present invention, in the method for molding a resin molded product according to any one of the first to fourth aspects, the foamable resin injection passage is provided in a front portion of the mold. And

  The invention of claim 6 is the method of molding a resin molded product according to any one of claims 1 to 5, wherein the injection port of the parison is formed before the injection port forming step. It is characterized in that a stress concentration portion where stress is concentrated when forming the inlet is formed in advance.

  According to a seventh aspect of the present invention, in the method for molding a resin molded product according to any one of the first to sixth aspects, a gas vent hole is formed in the parison before the start of the injection step. The foamable resin is injected while venting the gas in the parison from the vent hole.

  The invention according to claim 8 is the method of molding a resin molded product according to any one of claims 1 to 7, wherein the foamable resin contains a physical foaming agent.

  The invention according to claim 9 is the method for molding a resin molded product according to claim 8, wherein the physical foaming agent is a supercritical fluid.

  The invention of claim 10 is a molding apparatus for a resin molded product having an interior made of a foamable resin and a surface layer portion made of a solid resin, a parison hanging means for hanging the solid resin parison, and a molten foamable resin A mold having a foamable resin injection passage for guiding the gas into the cavity, mold clamping means for forming a bag shape with the suspended parison interposed therebetween, and blowing a gas into the bag-shaped parison, Blow shaping means for inflating the mold into the shape of the cavity of the mold, and after the blow shaping by the blow shaping means, the foaming resin injection passage of the parison by the gas used in the blow shaping Blowing the part connected to the inside from the inside to the outside, the injection port forming means for forming the injection port of the foamable resin, and the parison remain blown in the cavity. Is allowed, the molten foamable resin is injected into the foamable resin injection passage, characterized in that via the inlet including an injection means for injecting into the parison.

  According to an eleventh aspect of the present invention, there is provided the molding apparatus for a resin molded product according to the tenth aspect, wherein the foamable resin injection passage is provided with an injection passage valve for enlarging the cavity volume by moving the valve body. When the inlet is formed, the cavity volume is enlarged by the injection passage valve while the pressure in the parison is maintained, and the injection port is formed.

  According to a twelfth aspect of the present invention, in the molding apparatus for a resin molded product according to the eleventh aspect, the injection passage valve moves in the open state in which the foamable resin injection passage is opened, the first closed state in which the valve body moves. As a result, it is possible to switch from the first closed state to the second closed state that is closed with the cavity volume enlarged, and during the blow shaping, the first closed state is set, and the injection port is formed. The second closed state is sometimes used, and the opened state is used when the foamable resin is injected.

  A thirteenth aspect of the present invention is the molding apparatus for a resin molded product according to any one of the tenth to twelfth aspects of the present invention, wherein the molding die has a narrowed portion for thinning a parison at a location where the inlet is formed. It is characterized by having.

  A fourteenth aspect of the present invention is the molding apparatus for a resin molded product according to any one of the tenth to thirteenth aspects, wherein the foamable resin injection passage is provided in a front portion of the molding die. And

  A fifteenth aspect of the present invention is the molding apparatus for a resin molded product according to any one of the tenth to fourteenth aspects, wherein stress is concentrated at a position where the inlet of the parison is formed when the inlet is formed. Stress concentration portion forming means for forming the concentration portion in advance is provided.

  A sixteenth aspect of the present invention is the molding apparatus for a resin molded product according to any one of the tenth to fifteenth aspects, further comprising a gas vent hole forming means for forming a gas vent hole in the parison, wherein the injection means is foamed. When injecting the functional resin, the foamable resin is injected into the parison while venting the gas in the parison from the gas vent hole.

  According to a seventeenth aspect of the present invention, in the molding apparatus for a resin molded product according to any one of the tenth to sixteenth aspects, the foamable resin contains a physical foaming agent.

  According to an eighteenth aspect of the present invention, in the molding apparatus for a resin molded product according to the seventeenth aspect, the physical foaming agent is a supercritical fluid.

  According to the first aspect of the present invention, a lightweight resin molded product whose interior is made of a foamable resin can be obtained. And since the surface layer part consists of solid resin (parison), the bubble of an internal foamable resin is not exposed to the surface. Therefore, the beauty can be easily improved. Further, by appropriately setting the material and thickness of the skin, necessary physical properties (rigidity, etc.) can be easily obtained.

  And after a blow shaping process, the injection port of a foamable resin can be formed in a parison, without opening a mold by blowing a part of parison. For this reason, it can transfer to an injection process continuously following a blow shaping process, and can perform easy and efficient shaping | molding.

  According to the invention of claim 2, in the injection port forming step, the cavity volume is expanded in a state where the atmospheric pressure in the parison is maintained. Thereby, since the parison of the part connected to the foamable resin injection passage can further bulge outward, or more easily bulges, the parison can be blown through (formation of the injection port) more reliably.

  According to the invention of claim 3, the cavity volume can be expanded by switching the injection passage valve from the first closed state to the second closed state. Further, by subsequently switching the injection passage valve from the second closed state to the open state, it is possible to continuously shift from the foaming resin injection stop state to the injectable state.

  In other words, according to this injection passage valve, in addition to the action of expanding the cavity volume, in addition to the action of expanding the cavity volume, the action of opening and closing the foamable resin injection path, the expansion of the cavity volume and the injection and injection of the foamable resin are performed. The effect | action which enables it to perform continuously can also be acquired.

  According to the invention of claim 4, since the parison at the portion where the injection port is formed is thinned in the injection port forming step, it can be easily blown off. That is, the injection port can be formed in the parison more easily.

  According to the invention of claim 5, since the foamable resin can be injected from a position closer to the center of the molded product, the filling property can be easily improved.

  According to the invention of claim 6, since the stress concentration portion (for example, indentation or the like) is formed in advance at the injection hole forming portion of the parison, it becomes easy to blow the parison in the injection hole forming step. Therefore, the injection port can be formed more easily and reliably.

  According to the invention of claim 7, in the injection process, the gas in the parison is discharged via the vent hole. Accordingly, the filling of the foamable resin is suppressed from being inhibited by the gas used in the blow shaping process, and the filling property can be improved.

  According to the eighth aspect of the invention, the physical foaming agent can form a fine and uniform foamed cell structure, so that physical properties such as rigidity can be further improved.

  According to the ninth aspect of the present invention, the supercritical fluid having the properties that the density is close to that of a liquid and the fluidity is in a gaseous state actively moves in the molten resin during foaming and diffuses deep into the molecule. The effect of claim 7 can be further promoted.

  According to the tenth to eighteenth aspects of the present invention, it is possible to easily obtain a molding apparatus for a foamed resin molded product having the effects corresponding to the first to ninth aspects.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a resin molding product molding apparatus 1 (hereinafter abbreviated as molding apparatus 1) according to a first embodiment of the present invention. The molding apparatus 1 is a molding apparatus for obtaining a resin molded product having an inside made of a foamable resin and a surface layer portion made of a solid resin (non-foamable resin). As a use of such a resin molded product, for example, a trunk board of an automobile, which is required to have a certain level of rigidity and strength while being lightweight, and which is also required to have a beautiful appearance, is suitable.

  The molding apparatus 1 includes a mold clamping mechanism unit 10, an injection mechanism unit 30, and a blow mechanism unit 50 as its basic configuration.

  The mold clamping mechanism portion 10 (mold clamping means) is a mechanism that performs mold clamping and mold opening of the mold 2 by a hydraulic mechanism or an electric motor that is not shown in the drawing. It has the same configuration as the mold clamping mechanism used in the injection molding apparatus.

  The injection mechanism 30 (injection means) is a mechanism that injects the molten foamable resin 36 into the mold 2 (specifically, inside the parison P blow-molded in the cavity of the mold 2). .

  The injection mechanism unit 30 has the same configuration as an injection mechanism used in a general injection molding apparatus. Specifically, it includes a hopper 35 that is a supply port for the resin pellets 36a, and a cylinder 31 and a screw 33 that are heated downstream to plasticize (melt) the resin pellets 36a and draw them downstream while kneading. The tip of the cylinder 31 is connected to the mold 2. As a material of the resin pellet 36a, a thermoplastic resin such as polypropylene (PP) is preferable.

  Furthermore, about 20% of glass fibers (long fibers) may be mixed in the resin pellets 36a as reinforcing fibers. Instead of glass fibers, carbon fibers, nanofibers, fibrous or granular fillers, natural fibers, etc. May be used.

An SCF supply pipe 41 that supplies a supercritical fluid (SCF) 47 (hereinafter abbreviated as SCF47) used as a physical foaming agent is connected to a middle position of the cylinder 31 via a valve 40. The supercritical fluid (SCF47) is a known fluid that is in a supercritical state at a predetermined critical temperature or higher and a critical pressure or higher. The type of SCF 47 used in this embodiment is an inert gas, preferably carbon dioxide (CO ₂ ) or nitrogen (N ₂ ). The SCF 47 has a gas fluidity while having a density close to that of a liquid. The critical temperature of CO ₂ is 31 ° C., and the critical pressure is 7.4 MPa. N _{2 has} a critical temperature of −147 ° C. and a critical pressure of 3.4 MPa.

  The SCF 47 is stored in the SCF tank 48 via the SCF supply unit 45, and an appropriate amount of SCF 47 is sent to the SCF supply pipe 41 by the SCF supply unit 45. By opening the valve 40, the SCF 47 is mixed into the resin in the cylinder 31 to become a foamable resin 36.

  It should be noted that other physical foaming agents may be used in place of SCF47, and chemical foaming agent 36b that is thermally foamed by a chemical reaction instead of physical foaming agent (previously mixed in resin pellet 36a, for example, about 6%). May be used.

  The blow mechanism unit 50 hangs a solid resin cylindrical parison P toward the mold clamping mechanism unit 10 by extrusion molding, blows air into the parison P with a blow pin 64, and then expands the blow pin 64 to the parison P. Evacuate from inside. That is, the blow mechanism unit 50 includes a parison hanging means, a blow shaping means, and a blow pin retracting means. In this embodiment, air is used as the gas to be blown. In addition, nitrogen or the like may be used.

  The blow mechanism unit 50 has the same configuration as that of the mechanism used in a general blow molding apparatus. Specifically, a hopper 55 that is a supply port for resin pellets 57 (a material of parison P), a cylinder 51 and a screw that are heated and plasticized (melted) downstream of the resin pellets 57 and then drawn downstream while being kneaded. 53, a cylinder 60 for extruding the plasticized resin downward from the die 62 having an annular gap to suspend the cylindrical parison P, a blow pin 64 for blowing air, and an air for supplying air to the blow pin 64 Supply pipe 66.

  The cylinder 60 has a built-in mechanism for moving the blow pin 64 in the axial direction (vertical direction).

  As a material of the resin pellet 57 used as the material of the parison P, a thermoplastic resin such as polypropylene (PP) is preferable.

  2 and 3 are longitudinal sectional views around the mold 2 and are explanatory views sequentially showing the molding process by the molding apparatus 1. First, the structure of the mold 2 will be described with reference to these drawings. To do.

  As shown in FIG. 2A, the mold 2 (molding mold) mainly includes a first mold 3 and a second mold 4. At least one of the first mold 3 and the second mold 4 can be moved in the mold opening / closing direction (direction perpendicular to the hanging direction of the parison P) by the mold clamping mechanism 10. 2A shows a mold open state in which the first mold 3 and the second mold 4 are separated by a predetermined interval, and FIG. 2B shows the first mold 3 and the second mold 4. And shows a closed mold closed state.

  In the first mold 3 and the second mold 4, a mold surface 3a and a mold surface 4a are formed at positions facing each other. A space surrounded by the mold surface 3a and the mold surface 4a in the clamped state becomes the cavity 2a.

  As shown in FIG. 2A, a cylindrical parison P is suspended between the first mold 3 and the second mold 4 in the mold open state. A cylindrical blow pin 64 projects from the die 62 into the parison P. As described above, the blow pin 64 is movable up and down. In particular, the lower position is referred to as a blow position (the state shown in FIGS. 2A to 2C), and the upper position is referred to as a retracted position (the state shown in FIG. 3A).

  In the upper part of the mold surface 3a and the mold surface 4a, semicircular recesses 3b and 4b (gas vent hole forming means) are formed in plan view so as to follow the outer shape of the blow pin 64 at the blow position. Yes.

  In addition, a narrowed portion 3c that is further engraved than the shape of the molded product is formed in the approximate center of the mold surface 3a. An injection passage 3d (foamable resin injection passage) is provided which communicates the tip of the cylinder 31 with the throttle portion 3c and guides the molten foamable resin into the cavity 2a. The injection passage 3d is provided substantially at the center of the front portion of the first mold 3 as shown in the figure.

  An injection passage valve 5 is provided at the boundary between the throttle portion 3c and the injection passage 3d to connect and disconnect these connections. As shown in FIG. 2 (d), the injection passage valve 5 is a composite valve composed of a first valve 6 and a second valve 7. The first valve 6 causes the valve body 14 to open and close by extending and contracting the rod 13, the valve body 14 that directly connects and disconnects the throttle portion 3 c and the injection passage 3 d, the valve body 14, and the rod 13. Actuator 12. Although the details of the second valve 7 are omitted, the second valve 7 includes components corresponding to the valve body 14, the rod 13, and the actuator 12, similarly to the first valve 6.

  The injection passage valve 5 is configured such that the first valve 6 and the second valve 7 are both opened, and the throttle portion 3c and the injection passage 3d are in communication with each other (the state shown in FIG. 3C). The first valve 6 is opened while the second valve 7 is closed, as a result of the first closed state (the state of FIG. 2D) in which both the two valves 7 are closed and the throttle portion 3c and the injection passage 3d are shut off. It is possible to switch to the second closed state (the state shown in FIG. 2 (e)) that shuts off the throttle portion 3c and the injection passage 3d. In the first closed state, the valve body 14 of the first valve 6 forms the cavity 2a in the innermost portion of the throttle portion 3c. In the second closed state, when the valve body 14 moves downward (arrow A1), a space (first first) between the first valve 6 and the second valve 7 is newly added to the innermost part of the throttle portion 3c. (Including the space occupied by the valve body 14 in the closed state). That is, the cavity volume is expanded as compared with the first closed state. It can also be said that the aperture of the aperture 3c is deeper.

  Next, the operation of the molding apparatus 1 and the molding method using the molding apparatus 1 will be described with reference to FIGS.

  FIG. 2A shows a parison drooping process in which the parison P is drooped from the die 62. The mold 2 is opened, and the parison P is suspended between the first mold 3 and the second mold 4. The injection passage valve 5 is in the first closed state.

  FIG. 2B shows a mold clamping process in which the upper and lower sides of the suspended parison P are sandwiched between the first mold 3 and the second mold 4 to form a bag shape. The periphery of the blow pin 64 is surrounded by the recess 3b and the recess 4b with the parison P in between, and the bag-like parison P is kept airtight in this state. The tip of the blow pin 64 is open inside the parison P.

  This mold clamping process includes an air vent hole forming process. The air vent hole (gas vent hole; refer to P2 in FIG. 3D) is a hole for discharging air in the parison P in a later injection process. The air vent hole is formed by a parison P (formed by the recesses 3b and 4b) surrounding the blow pin 64 in the air vent hole forming step. However, at present, it is not actually a hole, but a latent hole.

  By performing the air vent hole forming step in the mold clamping process in this way, the cycle time can be shortened and the production efficiency can be increased as compared with the case where a separate air vent hole forming step is provided.

  FIG. 2C shows a blow shaping process in which the air B is blown into the bag-shaped parison P by the blow pins 64 to inflate the parison P into a shape along the cavity shape. The parison P is brought into close contact with the mold surface 3a and the mold surface 4a by the internal pressure of the air B, and is shaped.

  FIG. 2 (d) is an enlarged view around the injection passage valve 5 of FIG. 2 (c). The parison P is in close contact with the throttle 3c while being squeezed. For this reason, the parison P in the vicinity of the throttle portion 3c is thinner than the other portions.

  FIG. 2 (e) shows an injection port forming step in which, after the blow shaping step is completed, the cavity volume is enlarged and the portion facing the injection passage 3d of the parison is blown to become the injection port P9 of the foamable resin 36. In this injection port forming step, only the first valve 6 is opened (second closed state) while continuing to blow in the air B (maintaining the atmospheric pressure in the parison P). As shown in the figure, when the first valve 6 opens, that is, when the valve body 14 moves downward (arrow A1), a further space is created outside the parison P that is squeezed by the throttle portion 3c and thinned, and the cavity volume is increased. Expands. Thereby, the parison P of the throttle part 3c loses the support by the valve body 14 and further bulges out, and is blown away from the inside toward the outside to form the injection port P9.

  Thus, since the injection port P9 can be formed without opening the mold, it is possible to continuously shift from the blow shaping process to the injection process through the injection port forming process and the next blow pin retracting process. Therefore, efficient molding can be performed.

  Moreover, since the injection passage valve 5 including the valve body 14 that expands the cavity capacity is provided, the parison can be blown through (formation of the injection port) more reliably.

  In addition, since the injection port P9 is provided at the portion thinned by the throttle portion 3c, the injection port P9 can be formed by easily blowing the parison P.

  FIG. 3A shows a blow pin retracting process in which the blow pin 64 is retracted from the inside of the parison P after completion of the injection port forming process. When the inlet forming step is completed, the blowing of the air B is stopped, and the blow pin 64 moves to the upper retracted position (arrow A2). Then, the hole that has passed through the blow pin 64 remains until the blow pin 64 is retracted. This hole is a manifestation of the air vent hole formed in the air vent hole forming step (FIG. 2B) performed previously. Hereinafter, this hole is referred to as an air vent hole P2.

  Thus, since the hole remaining in the trace where the blow pin 64 is retracted becomes the air vent hole P2, there is no need to provide a separate air vent hole, and the process can be simplified and the production efficiency can be improved.

  The blow pin retracting step includes an air vent passage forming step. The air vent passage is a passage through which air in the parison P is discharged to the outside of the cavity 2a via the air vent hole P2 in a later injection process. In the present embodiment, the air vent hole P2 itself is an air vent passage P2 '. That is, the air vent passage P2 'is formed by retracting the blow pin 64 and revealing the air vent hole P2.

  Further, by retracting the blow pin 64 to the retracted position, the blow pin 64 is effectively prevented from being clogged by the foamable resin 36 in the subsequent injection process.

  FIG. 3B shows the start point of the injection process of injecting the foamable resin 36 melted into the parison P after the blow pin retracting process is completed. In the injection process, the injection passage valve 5 is opened. That is, the second valve 7 is opened while the first valve 6 continues to open (arrow A2). As a result, the foamable resin 36 can be injected from the injection passage 3d into the cavity 2a (inside the parison P) via the injection port P9.

  Thus, according to the injection passage valve 5, in addition to the operation of expanding the cavity volume, the operation of opening and closing the foamable resin injection passage, the expansion of the cavity volume, and the injection / injection of the foamable resin, although having a simple structure. It is also possible to obtain an action that enables continuous operation.

  FIG. 3C shows an initial stage of the injection process. The foaming resin 36 is injected from the tip of the cylinder 31 by the injection mechanism 30, and injection and filling into the parison P are started.

  FIG. 3D shows the middle stage of the injection process. As the filling of the foamable resin 36 into the parison P proceeds, the air B in the parison P is discharged through the air vent hole P2 (air vent passage P2 '). Thus, since the replacement of the air B and the foamable resin 36 is appropriately performed in the parison P, it is possible to suppress the filling of the foamable resin 36 from being inhibited by the air B and to improve the fillability.

  In addition, since the injection passage 3d is provided at substantially the center of the front portion of the first mold 3, the foamable resin 36 can be injected from a position closer to the center of the molded product, and the filling property is further improved. ing.

  FIG. 3E shows a mold opening process after the injection process is completed. When a predetermined amount of the foamable resin 36 is injected, the injection passage valve 5 is closed (arrow A4, first closed state), and the injection process is completed. Thereafter, the mold 2 is opened after a predetermined cooling period, and the molded product M is taken out.

  FIG. 4 is a perspective view of the molded product M having a partial cutout. Through the above steps, a molded product M is obtained which is made of the foamable resin 36 inside and the surface layer portion made of solid resin 67 (Parison P).

  The molded product M is lightweight because its inside is made of the foamable resin 36. In addition, high air filling performance is obtained because appropriate air venting is performed in the injection process. Since SCF47 (supercritical fluid) is used as the physical foaming agent, a fine and uniform foamed cell structure is formed by SCF47 that diffuses deep into the molecule. Accordingly, high physical properties (such as rigidity) can be obtained.

  Further, since the surface layer portion of the molded product M is made of the non-foamable solid resin 67, the bubbles of the foamable resin 36 inside are not exposed on the surface. Therefore, the aesthetics are enhanced. In addition, by appropriately setting the material and thickness of the parison P, necessary physical properties (rigidity, etc.) can be easily obtained.

  After the state shown in FIG. 4, the molded product M is appropriately finished by removing unnecessary portions (air vent hole P2, surplus parison P3 (burr), injection mark P4, etc.).

  FIG. 5 is a partial cross-sectional view around the injection passage valve 5a of the molding apparatus 1 according to the second embodiment of the present invention, in which (a) is a blow shaping process, (b) is an injection port forming process, c) shows the initial stage of the injection process, and (d) shows the completion point of the injection process. (E) is a partial cross-sectional view of the molded product M1 obtained after completion of the injection process. In the drawings showing the following embodiments, members having the same or similar functions as those in the drawings showing the first embodiment are denoted by the same reference numerals, and redundant description thereof is omitted.

  In the first embodiment, the throttle portion 3c of the first mold 3 is provided at a position on the outer side of the molded product, whereas in the present embodiment, it is provided at a position to be buried inside the molded product. That is, a cylindrical protrusion 3e is formed in the first mold 3 so as to protrude toward the molded product, and its inner diameter portion is a throttle portion 3c.

  Moreover, the point by which the injection | pouring passage valve 5a is comprised with the single valve differs from 1st Embodiment. For the sake of simplicity, only the valve body of the injection passage valve 5a is shown in FIG. The injection passage valve 5a (the valve body) moves in the mold opening / closing direction and is switched in three stages. When the injection passage valve 5a is located closest to the cavity 2a (the state shown in FIG. 5A), the first closed state in which the communication between the throttle portion 3c and the injection passage 3d is cut off is established. In addition, the front end surface (surface facing the parison P) of the injection passage valve 5a at this time is at a position corresponding to the outer shape of the molded product.

  When the injection passage valve 5a is second closest to the cavity 2a (the state shown in FIG. 5B), the second closed state in which the communication between the throttle portion 3c and the injection passage 3d is blocked. In the second closed state, the cavity volume is enlarged compared to the first closed state. It can be said that the aperture of the aperture 3c is deeper.

  When the injection passage valve 5a is farthest from the cavity 2a (the state shown in FIG. 5C), the throttle portion 3c and the injection passage 3d are in an open state.

  In the blow shaping step shown in FIG. 5A, the injection passage valve 5a is in the first closed state. The parison P is deformed along the shape of the projecting portion 3e due to the blowing of the air B, and is squeezed and thinned by the throttle portion 3c.

  In the injection port forming step shown in FIG. 5B, the air B is continuously blown (atmospheric pressure in the parison P is maintained) and the injection passage valve 5a is brought into the second closed state. Thereby, the parison P of the throttle portion 3c loses the support by the injection passage valve 5a and further bulges, and is blown off from the inside toward the outside to form the injection port P9.

  In the initial stage of the injection process shown in FIG. 5C, the blowing of the air B has already been stopped in the previous blow pin retracting process. The injection passage valve 5a is opened, and the foaming resin 36 is injected from the tip of the cylinder 31 by the injection mechanism 30, and injection and filling into the parison P are started.

  When the injection process shown in FIG. 5D is completed, the injection passage valve 5a is in the first closed state, and the injection of the foamable resin 36 is stopped.

  As shown in FIG. 5E, the molded product M1 obtained through the above steps is characterized in that the injection mark P4 does not protrude from the outer shape of the molded product M1. Although a concave mark due to the protrusion 3e of the first mold 3 remains around the injection mark P4, if this is acceptable, the removal process is performed as compared with the case where the injection mark P4 protrudes as in the first embodiment. There is an advantage that it can be omitted.

  Further, the injection passage valve 5a has a longer stroke than the injection passage valve 5 of the first embodiment, but can obtain the same operation and effect as the injection passage valve 5 with a simpler structure. There is an advantage that can be.

  FIG. 6 is a partial cross-sectional view around the injection passage valve 5b of the molding apparatus 1 according to the third embodiment of the present invention, where (a) is a blow shaping process, (b) is an injection port forming process, c) shows the initial stage of the injection process, and (d) shows the completion point of the injection process. (E) is a partial cross-sectional view of a molded product M2 obtained after completion of the injection process.

  In the present embodiment, similarly to the second embodiment, a cylindrical protruding portion 3e is formed so as to protrude from the first mold 3 toward the molded product, and the inner diameter portion serves as a throttle portion 3c. The structure of the injection passage valve 5b is substantially the same as that of the injection passage valve 5a of the second embodiment, but the injection passage valve 5b of this embodiment has a parison P on the tip side (a side facing the parison P). The point which has the pointed part 58 (stress concentration part formation means) sharpened toward is different from 2nd Embodiment.

  The injection passage valve 5b moves in the mold opening / closing direction and is switched in three stages. When the injection passage valve 5b is in the position closest to the cavity 2a (the state shown in FIG. 6A), the first closed state in which the communication between the throttle portion 3c and the injection passage 3d is blocked. At this time, the pointed end portion 58 of the injection passage valve 5b is located at a position that enters the inside of the molded product from the tip end portion of the protruding portion 3e. For this reason, the parison P is squeezed and thinned on the side opposite to the squeezing direction in the squeezing portion 3c (inward of the cavity 2a).

  When the injection passage valve 5b is second closest to the cavity 2a (the state shown in FIG. 6B), the second closed state in which the communication between the throttle portion 3c and the injection passage 3d is interrupted. In the second closed state, the cavity volume is enlarged with respect to the first closed state. It can also be said that the parison P is released from the stop by the pointed portion 58 and is deepened further by the restricting portion 3c on the opposite side. Further, the base point of the inclined portion of the tip portion 58 is at a position substantially corresponding to the outer shape of the molded product.

  When the injection passage valve 5b is located farthest from the cavity 2a (the state shown in FIG. 6C), the throttle portion 3c and the injection passage 3d are in an open state.

  In the blow shaping process shown in FIG. 6A, the injection passage valve 5b is in the first closed state. The parison P is deformed along the shape of the protruding portion 3e by the blowing of the air B, and is thinned. Then, an indentation (stress concentration portion P10) is attached by the pointed portion 58 protruding from the protruding portion 3e.

  In the injection port forming step shown in FIG. 6B, the air B is continuously blown (atmospheric pressure in the parison P is maintained) and the injection passage valve 5a is brought into the second closed state. As a result, the parison P of the throttle portion 3c loses its support by the injection passage valve 5b and further bulges out, and blows away from the inside toward the outside to form the injection port P9. At that time, stress concentration occurs in the stress concentration portion P10 provided in the blow shaping step, and the material is easily blown away. Therefore, the injection port P9 can be formed easily and reliably.

  In the initial stage of the injection process shown in FIG. 6C, the blowing of the air B has already been stopped in the previous blow pin retracting process. The injection passage valve 5b is opened, and the foaming resin 36 is injected from the tip of the cylinder 31 by the injection mechanism 30 to start injection and filling into the parison P.

  At the time when the injection process shown in FIG. 6D is completed, the injection passage valve 5b is in the second closed state, and the injection of the foamable resin 36 is stopped.

  As shown in FIG. 6E, the molded product M2 obtained through the above steps is characterized in that the injection mark P4 does not protrude from the outer shape of the molded product M2. A concave mark due to the protrusion 3e of the first mold 3 remains around the injection mark P4, and a concave mark due to the pointed portion 58 of the injection passage valve 5b remains in the injection mark P4. There is an advantage that the removal process can be omitted as compared with the case in which the injection mark P4 protrudes as in the first embodiment.

  In addition, the injection passage valve 5b has an advantage that a function of easily forming the stress concentration portion P10 can be added to the injection passage valve 5a of the second embodiment by a simple structural change. Moreover, since the thinning by the pointed portion 58 is achieved, the blow-off property of the parison P can be improved as compared with the case where the tip is flat.

  The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention described in the claims. For example, materials other than those described above may be used for the foamable resin 36 and the parison P.

  In addition, the stress concentration portion P10 shown in the third embodiment is not necessarily an indentation by the pointed portion 58, and may be any as long as it causes some stress concentration such as a flaw to easily blow the parison P.

  Further, it is not always necessary to provide an injection passage valve that enlarges the cavity volume. For example, in the first embodiment, the injection passage valve 5 may be configured to include only the second valve 7 by omitting the first valve 6. In this way, a sufficiently deep throttle portion 3c is formed, and the injection passage valve 5 is switched in two steps between an open state and a closed state (first closed state) (the injection passage valve 5 has an effect of expanding the cavity volume). lose). In this case, the blow shaping step and the injection port forming step are performed with the injection passage valve 5 closed. First, in the blow shaping process, when the parison P enters a certain depth of the narrowed portion 3c, the blow shaping of other parts is completed (the process shifts from the blow shaping to the inlet forming process at this point). To do). Further, by continuing the blowing of air B (maintaining the atmospheric pressure in the parison P), only the parison P of the constricted portion 3c with the bulge space further bulges and blows away from the inside toward the outside, P9 is formed.

  Such a form may be applied when the molded product M has a relatively simple shape (when the shaping of another portion is completed before the parison P is blown through). In other words, when the molded product M has a relatively complicated shape, the injection port P9 can be more reliably formed after blow molding by providing the injection passage valve 5 that expands the cavity volume.

It is a schematic block diagram of the molding apparatus of the resin molded product which concerns on 1st Embodiment of this invention. It is a longitudinal cross-sectional view around the metal mold | die of the apparatus shown in FIG. 1, Comprising: It is explanatory drawing which shows a formation process in order. (A) is a parison dripping process, (b) is a mold clamping process, (c) is a blow shaping process, and (e) is an injection port forming process. (D) is the elements on larger scale of (c). FIG. 3 is a longitudinal sectional view around a mold of the apparatus shown in FIG. 1, and is an explanatory view sequentially showing molding steps subsequent to FIG. 2. (A) is a blow pin retracting process, (b) is a starting point of the injection process, (c) is an initial stage of the injection process, (d) is a middle stage of the injection process, and (e) is a mold opening process. It is a perspective view which has a notch of a molded article. It is a fragmentary sectional view around an injection passage valve of a molding device concerning a 2nd embodiment of the present invention, (a) is a blow shaping process, (b) is an injection hole formation process, (c) is an injection process. The initial stage, (d) shows the completion point of the injection process. (E) is a fragmentary sectional view of the molded product obtained after completion of the injection process. It is a fragmentary sectional view around an injection passage valve of a forming device concerning a 3rd embodiment of the present invention, (a) is a blow shaping process, (b) is an injection hole formation process, (c) is an injection process. The initial stage, (d) shows the completion point of the injection process. (E) is a fragmentary sectional view of the molded product obtained after completion of the injection process.

Explanation of symbols

1 Molding device for resin molded products 2 Mold (molding die)
2a Cavity 3b Concave (gas vent formation means)
3c restrictor 3d injection passage (foamable resin injection passage)
4b Recess (gas vent formation means)
5 Injection passage valve, injection port forming means 5a, 5b Injection passage valve, injection port forming means, valve body 10 Mold clamping mechanism (mold clamping means)
14 Valve body 30 Injection mechanism part (injection means)
36 Foamable resin 47 Supercritical fluid (physical foaming agent)
50 Blow mechanism (Parison drooping means, blow shaping means, blow pin retracting means)
58 Tip (stress concentration part forming means)
64 Blow pins 67 Solid resin (Parison)
B Air (gas)
P Parison P2 Air vent hole (gas vent hole)
P9 Inlet P10 Stress concentration part

Claims (18)

A molding method of a resin molded product, the inside of which is made of a foamable resin and the surface layer portion is of a solid resin,
A parison drooping process for dripping the solid resin parison;
A mold clamping step for forming a bag shape with the parison suspended, with a molding die having a foamable resin injection passage for guiding the melted foamable resin into the cavity,
Blow shaping step of blowing gas into the bag-shaped parison and inflating the parison into a shape along the cavity shape of the mold,
After completion of the blow shaping process, the gas used in the blow shaping process blows off the portion of the parison that leads to the foamable resin injection passage from the inside to the outside, and serves as an inlet for the foamable resin. An entrance formation process;
An injection step of allowing the parison to remain in the cavity in a blow-molded state, injecting the molten foamable resin into the foamable resin injection passage, and injecting into the parison via the injection port A method for molding a resin molded product comprising: The foamable resin injection passage is provided with an injection passage valve that expands the cavity volume by moving the valve body,
2. The molding of a resin molded product according to claim 1, wherein the injection port is formed by expanding the cavity volume by the injection passage valve while maintaining the pressure in the parison in the injection port forming step. Method.   The injection passage valve is closed in an open state in which the foamable resin injection passage is opened, in a first closed state in which the foamable resin injection passage is closed, and in a state in which the cavity volume is larger than that in the first closed state due to movement of the valve body. 2 can be switched to the closed state, the first closed state in the blow shaping step, the second closed state in the injection port forming step, and the open state in the injection step. The method for molding a resin molded product according to claim 2, wherein:   The method for molding a resin molded product according to any one of claims 1 to 3, wherein the molding die has a narrowed portion for thinning a parison at a location where the injection port is formed.   The method for molding a resin molded product according to any one of claims 1 to 4, wherein the foamable resin injection passage is provided in a front portion of the mold.   6. The stress concentration part where stress is concentrated at the time of forming the injection port is formed in advance at the location where the injection port of the parison is formed before the injection port forming step. The molding method of the resin molded product of any one of Claims 1. Before the start of the injection process, a vent hole is formed in the parison,
The method for molding a resin molded product according to any one of claims 1 to 6, wherein in the injection step, the foamable resin is injected while venting the gas in the parison from the gas vent hole.   The method for molding a resin molded product according to claim 1, wherein the foamable resin contains a physical foaming agent.   9. The method for molding a resin molded product according to claim 8, wherein the physical foaming agent is a supercritical fluid. A molding apparatus for a resin molded product having an interior made of a foamable resin and a surface layer portion made of a solid resin,
A parison drooping means for dripping the solid resin parison;
A mold clamping means having a foamable resin injection passage for guiding the melted foamable resin into the cavity, and mold-clamping means for forming a bag shape with the suspended parison interposed therebetween,
Blow shaping means for blowing gas into the bag-shaped parison, and inflating the parison into a shape along the cavity shape of the mold,
After blow shaping by the blow shaping means, the gas used in the blow shaping is blown from the inside to the outside of the parison leading to the foamable resin injection passage, An injection port forming means,
Injection means for allowing the parison to remain in the cavity in a blow-shaped state, injecting the molten foamable resin into the foamable resin injection passage, and injecting it into the parison via the injection port An apparatus for molding a resin molded product, comprising: The foamable resin injection passage is provided with an injection passage valve that expands the cavity volume by moving the valve body,
11. The resin molded product according to claim 10, wherein when the injection port is formed, the injection port is formed by expanding the cavity volume with the injection passage valve in a state where the pressure in the parison is maintained. Molding equipment.   The injection passage valve is closed in an open state in which the foamable resin injection passage is opened, in a first closed state in which the foamable resin injection passage is closed, and in a state in which the cavity volume is larger than that in the first closed state due to movement of the valve body. 2 can be switched to the closed state, the first closed state during the blow molding, the second closed state when the injection port is formed, and the open state during the injection of the foamable resin. The apparatus for molding a resin molded product according to claim 11, wherein:   The apparatus for molding a resin molded product according to any one of claims 10 to 12, wherein the molding die has a narrowed portion for thinning a parison at a location where the injection port is formed.   The apparatus for molding a resin molded product according to any one of claims 10 to 13, wherein the foamable resin injection passage is provided in a front portion of the mold.   15. The stress concentration portion forming means for previously forming a stress concentration portion where stress concentrates at the time of forming the injection port at a location where the injection port of the parison is formed. The molding apparatus of the resin molded product as described in 2. A gas vent forming means for forming a gas vent in the parison is provided.
16. The foamable resin is injected into the parison while venting the gas in the parison from the gas vent hole when the injection means injects the foamable resin. The molding apparatus of the resin molded product as described in 2.   The molding apparatus for a resin molded product according to any one of claims 10 to 16, wherein the foamable resin contains a physical foaming agent.   The apparatus for molding a resin molded product according to claim 17, wherein the physical foaming agent is a supercritical fluid.

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